1. Field of the Invention
The present invention relates to a method of forming an ozonetetraethylorthosilicate (O3-TEOS) oxide film, and to apparatus for depositing material, such as O3-TEOS oxide, on a substrate.
2. Description of the Related Art
As of recent, TEOS oxide films are being widely used as interlayer dielectric films and planarization films of semiconductor devices. O3-TEOS oxide films, which comprise a TEOS film formed using ozone (O3) as a catalyst, are also being widely used for such applications.
General TEOS films have a step coverage superior to that of conventional exhibits a smooth shape at the edges of an underlying pattern layer and excels in filling the gap between adjacent portions of the pattern layer. Moreover, O3-TEOS films have excellent characteristics when serving as planarization films. However, when TEOS films are formed on an underlying film, they may exhibit an abnormal growth pattern or poor surface characteristics, depending on the type of material or pattern of the underlying film. That is, the dependence of the quality of O3-TEOS films upon their underlying films includes pattern dependence (or pattern sensitivity) and base material dependence. Pattern dependence refers to the fact that O3-TEOS deposits relatively slowly over dense patterns and much quicker over sparse patterns; consequently, an O3-TEOS film typically will have a non-uniform thickness when deposited over an underlying pattern layer. Base material dependence refers to the fact that O3-TEOS can grow irregularly or acquire an excessive surface roughness depending on the material of its underlying film, independently of the density of patterns of the underlying film.
The present invention particularly relates to the base material dependence of O3-TEOS films. The base material dependence of O3-TEOS films will now be described in further detail with reference to FIG. 1.
As shown in this figure, a layer 13 having a predetermined pattern is formed on a substrate 11 (a silicon substrate or a layer of material already formed on a substrate). A lower film 15 of a material for which O3-TEOS exhibits base dependence is then formed on the resultant substrate. An O3-TEOS film 17 is then formed on the lower film 15. As shown in FIG. 1, the O3-TEOS film 17 forms unevenly on the lower film, and has an extremely rough surface due to abnormal growth. Here, it must be noted that the high surface roughness is not due to the pattern of the underlying layer 13 but due to the material of the lower film 15 on which the O3-TEOS film 17 is formed. In fact, even if the O3-TEOS film 17 were formed on a flat underlying layer 13 instead of one having a stepped configuration as shown in FIG. 1, only the pattern dependence of the O3-TEOS film 17 would be reduced and the film would still exhibit base dependence problems similar to those described above. Films for which an O3-TEOS film has base material dependence include a thermal oxide film, a high temperature oxide (HTO) film, a nitride film formed by chemical vapor deposition (CVD), and a TEOS film formed by plasma enhanced CVD (PE-CVD). Finally, it should be noted that the cause of base material dependence is assumed to be some characteristic of the underlying film, e.g., hydrophilicity/hydrophobicity, or the existence of an ON group, but such a cause has not yet been ascertained with a high degree of certainty.
Regardless, base material dependence can be eliminated by the following three proposed methods.
First, a lower film 15 of a material for which the O3-TEOS film 17 has no base material dependence can be formed on the substrate just prior to the depositing of the O3-TEOS film 17. For example, this material can be an oxide deposited by PE-CVD using a silane gas as a source gas, or a nitride deposited by PE-CVD (see U.S. Pat. No. 5,804,498 entitled xe2x80x9cMethod Of Making An Underlayer To Reduce Pattern Sensitivity Of Ozone-TEOSxe2x80x9d). Although this patent refers to pattern sensitivity, strictly speaking, what has been eliminated by the nitride or oxide formed by PE-CVD is base material dependence. However, since the PE-CVD oxide or nitride is formed by plasma deposition, the quality of its material is poor. Furthermore, PE-CVD is a complicated method to perform, and it is difficult to produce an oxide or nitride layer having a uniform thickness using PE-CVD. Therefore, the use of these materials as the film underlying the O3-TEOS film makes for unreliable semiconductor devices.
Secondly, the underlying film on which the O3-TEOS film has base material dependence may be plasma-treated for a predetermined period of time under an N2 or NH3 gas atmosphere, before the O3-TEOS is deposited thereon (see K. Fujino, Y. Nishimoto, N. Tokumasu, and K. Maeda, xe2x80x9cSurface Modification of Base Materials for TEOS/O3 Atmospheric Pressure Chemical Vapor Depositionxe2x80x9d, J. Electrochem. Soc., Vol. 139, No. 6, June 1999). The surface roughness of the O3-TEOS film 18 is significantly kept in check in this way, as shown in FIG. 2. However, plasma treatment is another complex processing method, and detracts from the productivity of the overall manufacturing process.
Thirdly, the O3-TEOS film may be deposited on the substrate at a high temperature. That is, O3-TEOS films are typically formed at about 400xc2x0 C. However, it has been shown that an O3-TEOS film formed at about 500xc2x0 C. has an excellent surface roughness. Unfortunately, this method is problematic in that the deposition rate is very slow and thus the method is associated with poor productivity. For example, when O3-TEOS is deposited on a bare silicon substrate at 400xc2x0 C., the deposition rate is approximately 800 xc3x85/min, but at 500xc2x0 C., the deposition rate is only about 150 xc3x85/min. Therefore, this third method is not suitable for mass production.
Accordingly, a first object of the present invention is to provide a simple method of depositing O3-TEOS, in which base material dependence is eliminated, and film quality and productivity are guaranteed.
The second object of the present invention is to provide a deposition apparatus which is particularly suitable for performing the above-described O3-TEOS deposition method and can also be used to deposit other materials on a substrate.
To achieve the first object, the present invention provides a method of forming an O3-TEOS oxide film which includes depositing a first portion of O3-TEOS oxide on a lower film, at such a high temperature that the characteristics of the O3-TEOS oxide film are not base material dependent on the lower film, and then depositing a second portion of O3-TEOS oxide on the first portion of O3-TEOS oxide at a low temperature which allows the deposition to occur at a high rate.
The temperature at which the first portion of the O3-TEOS oxide film is formed is preferably within a range of 450 to 600xc2x0 C., and the temperature at which the second portion of the O3-TEOS oxide film is preferably within a range of 360 to 440xc2x0 C. Also, such temperature conditions can be produced as a series step-wise temperature changes or as a continuously decreasing temperature.
Also, the deposition steps are preferably performed in situ to enhance productivity.
To achieve the second object, the present invention provides a deposition apparatus which includes at least two susceptors, each of which is configured to support a wafer on which a layer is to be formed and comprises a heater for heating the wafer, at least one shower head for directing source gases toward the wafers, and a robot arm for loading the susceptors with wafers, transferring the wafers between the susceptors, and unloading completed wafers from the susceptors. The temperature of at least one of the heaters can heat the wafer supported on its susceptor to a temperature different from that/those provided by the other heater/heaters.
To achieve the second object, the present invention also provides a deposition apparatus which includes a conveyor comprising at least one wafer tray configured to support a wafer and linearly movable in a horizontal direction along a conveyance path, at least-two wafer heaters fixed in place under the conveyance path and positioned relative to one another along the path of conveyance of the wafer tray, at least one shower head disposed over the conveyance path for supplying source gases of a material to be deposited on the wafers, and a robot arm for loading the at least one wafer tray with wafers and unloading the wafers from the wafer tray. Again, the temperature of at least one of the heaters can heat the wafer passing thereover to a temperature different from that/those provided by the other heater/heaters.
Accordingly, the deposition apparatus enable material to be deposited on a wafer at different temperatures, and as such, are effective in forming a high quality O3-TEOS oxide film on a wafer with a high rate of production.